To ask a Spaniard to name his favorite bocadillo is to invite a long and enthusiastic response likely to be as nostalgic as it is mouth watering. A sandwich traditionally made with crusty baguette bread, the unpretentious bocadillo is an integral part of the Spanish diet. Some 3.5 billion of them are served up each year at breakfast, lunch, dinner and snacktime. From the simple serranito (slices of ham squeezed between fat chunks of bread) to the filling and flavor-packed bocadillo de calamares (a baguette stuffed with fried calamari), they come in an endless and ever-changing variety.

"Sometimes we think that good food has to be sophisticated or complicated, but in all of us there's a nostalgia for simple, sincere flavors," says food writer and epicurean Mauricio Wiesenthal. "The bocadillo brings together the three bases of Mediterranean cuisine: wheat, olive oil, and wine (to accompany the sandwich). From there, we can incorporate all kinds of traditional flavors: Ibérico or Serrano ham and cured meats, cheese, peppers, tuna, sardines, tortilla de patatas (potato omelet), olives, whatever we want," he says. Although the most traditional bocadillos are filled with typical Spanish products, there's no limit to the creative spin modern chefs are putting on this old standard. From kneading squid ink into the bread, to incorporating international flavors like hummus or pesto, today's restaurants offer decidedly twenty-first century versions of the bocadillo alongside traditional favorites.

"In Spain we're lucky to have all kinds of magnificent ingredients, and today's sandwiches reflect that," says Mario Cañizal, the founder of the Bocadillo of the Year contest, now in its fifth edition. "We're in a transcendental moment for the sandwich in Spain. People are finding themselves with less and less time to eat, so the bocadillo is taking the place of the typical sit-down lunch. But incorporating nutritious, flavorful ingredients not on a plate but in a bocadillo requires creativity."

Fast Good, a fast-food chain born of a collaboration between NH Hotels and chef Ferran Adrià, epitomizes the new wave in bocadillos. With a vision of creating healthy, highquality food-to-go, the chain specializes in quick gourmet fare based on sandwiches and salads.

"Sixty years ago, my grandmother ate a bocadillo made with whatever was left in the kitchen, but these days people want something more," says Carlos Peguero, Fast Good's head chef. "Even if they work and don't have much time, they want something fresh and healthy."

In a trend seen across Spain, Fast Good's bocadillos combine traditional Spanish ingredients with international flavors, as in the bocatini, a croissant-style bread served with soft Sobrassada sausage, Manchego cheese, honey and lettuce. "In one way it's typically Mallorcan, but we've made it our own with a special bread," Peguero says.

Popular myth generally credits the invention of the sandwich to the 18th-century British Earl of Sandwich, who supposedly requested that his meals be served between two slices of bread so that he wouldn't have to interrupt card games. The story is debatable, but what food historians do agree on is that the bocadillo, (a derivation of the word bocado – a bite or a mouthful), likely began as a way to pair kitchen scraps or leftovers with bread. Through the years, however, it has evolved into an elaborate food category in its own right. Here's a sampling of some of Spain's most popular combinations.

Ham & Sausage Bocadillos
Cured meats like Ibérico and Serrano ham, chorizo, fuet, and lomo are foundations of the bocadillo. Served with or without cheese on bread that's been generously drizzled with extra virgin olive oil, the sandwiches are easy to make and are ubiquitous in restaurants, bars and homes across Spain.

"Ibérico ham is the king of bocadillos," Cañizal says. "My favorite is bread smeared with tomato, drizzled with olive oil and topped with a good ham. It's simple, but delicious. The trick is finding the best ingredients -- the best bread, the best oil, the best ham."

Bocadillo lover Tamar Guix recommends salchicha con queso, grilled sausage with cheese. "The best place to eat it is in one of those corner bars that looks like it's been open for 50 years. If you eat it anywhere else it's just not as good," she says.

Seafood Bocadillos
Golden rings of fried calamari, topped with a bit of mayonnaise and served up hot and juicy on baguette bread is a time-honored tradition in the plazas of Spain, especially in Madrid and Zaragoza.

You can also make it at home. "Our Mom's fried calamari sandwich is extraordinary," say brothers Alvaro and Daniel Liñán. "First cut the calamari into thin strips. Chop an onion and fry until golden, then add the calamari. Add salt, pepper and a bit of white wine to the pan. Slice open a wide baguette that's not too soft, and stuff it with the fried onions and calamari. Enjoy!"

"The real trick is the bread," adds Alvaro. "If the bread is bad, it doesn't matter what you put on the bocadillo, it won’t taste good."

Eugenio Berruezo, a bocadillo aficionado, says his mouth waters simply talking about the "Surf & Turf", made with grilled or canned sardines. "It should be made on bread that's been smeared with a juicy tomato and sprinkled with a little olive oil. Top with two or three slices of grilled bacon, and fillets of sardine. It's a complete sensory experience." Wiesenthal, the food writer, recommends combining tuna, grilled or canned peppers, and olives. "It's a fantastic flavor," he raves.

Bocadillo de Tortilla
"For me, it doesn't get any better than a sandwich made with tortilla de patata," Wiesenthal says. "You can add onion for a slightly sweet flavor, but it's important that the tortilla be cold so the flavors mix." Nearly anything can be added to the omelet to add flavor. Cheese and grilled vegetables are among the most common additions.

"I love bocadillos made with wild asparagus omelets," says self-proclaimed bocadillo expert Lluís Moncusí. "They're best in March or April, when you've gone into the countryside to hunt for wild asparagus and you can eat the fruits of your labor. To make one, first clean the asparagus and cut it into pieces. Throw it into the frying pan with a bit of olive oil and after three minutes add a couple of wellbeaten eggs. Serve it on bread with a bit of tomato and olive oil."

Pepito de Ternera
Cadiz's Bar Lucero is a mecca for lovers of the Pepito de Ternera grilled veal sandwich. This simple but tasty creation has been served here since the bar opened a half century ago and has even inspired a club of devotees, the Association of Pepito de Ternera Lovers, who hope to have 2012 declared the year of their favorite sandwich. "The trick is that the meat be really good quality and very tender, with the right amount of garlic and a good olive oil," says Lucero's manager, Fernando González. "That, and that you make it with love."

Other grilled meats make popular bocadillo fillings as well. The lomo con queso (grilled pork loin with cheese) is always a favorite. "It's a typical lunch sandwich – tasty and with proteins so you can get on with your day," says Moncusí.

Sweet Sandwiches
Not everything in the bocadillo universe is savory. Sweet sandwiches are a favorite snack.

"The best sandwich of my life was the one made with whipped cream (from fresh, whole milk) and chocolate bars that we had at home when I was a child," says Rosina Rodriguez. "Delicious!"

Paco Mateu recommends the Bocadillo de Sobrassada and Sugar. "It's simple: spread the sobrassada (a soft, tangy sausage) over a slice of brown bread and spread sugar on top. It's a typical afternoon snack in Mallorca." Vary the recipe by substituting sugar for honey.

Travel writer Sarah Andrews hails from North Carolina, but she’s been living in and writing about Spain since 2000, producing articles and guidebooks from her office near Barcelona. Visit her online at www.sarahandrews.com.